Oxidation makes the skin look cloudy and dull. If your airstream has the plasticoat still on it, it may look dull, but a good washing and waxing should revive it, as it did my 82.
The plasticoat if worn off or stripped off, will leave the bare aluminum which gets dull and cloudy and must be polished to regain a shine. It will depend on how much elbow grease and effort is put in as to how shiny it gets. Then it must be re-coated, so it does not have to be repolished ....although I think the polish and then a good wax job frequently will keep it looking pretty nice.
Mine has some small areas with no plasticoat, but most of it is still coated. I wax it with non abrasive turle wax liquid, and it seems to hold up for about 3 to 4 months. The small non coated areas I polished by hand, just for grins and they shine a bit more, but add to the overall look. Someday I might strip and polish the whole thing....but I know I will need darker sun glasses to look at it!!